Doc updates for buffer-stale-function now applying to file buffers too

* doc/emacs/arevert-xtra.texi (Supporting additional buffers):
* doc/lispref/backups.texi (Reverting):
Update for buffer-stale-function also applying to file-buffers.

* lisp/autorevert.el (auto-revert-buffers):
* lisp/files.el (buffer-stale--default-function)
(buffer-stale-function, revert-buffer--default): Doc tweaks.

* etc/NEWS: Related edits.

4 files changed, 10 insertions, 4 deletions

diff --git a/doc/emacs/ChangeLog b/doc/emacs/ChangeLog
index bd593f49db3..c0581424833 100644
--- a/doc/emacs/ChangeLog
+++ b/doc/emacs/ChangeLog
@@ -3,6 +3,8 @@
         * files.texi (Backup Names):
         * arevert-xtra.texi (Supporting additional buffers):
         Update for default values of some -function vars no longer being nil.
+        (Supporting additional buffers):
+        Update for buffer-stale-function also applying to file-buffers.
 
 2014-03-16  Dmitry Gutov  <dgutov@yandex.ru>
 
diff --git a/doc/emacs/arevert-xtra.texi b/doc/emacs/arevert-xtra.texi
index 0f05d1db0e1..dcb73bc96de 100644
--- a/doc/emacs/arevert-xtra.texi
+++ b/doc/emacs/arevert-xtra.texi
@@ -107,11 +107,11 @@ To support auto-reverting the buffer must first of all have a suitable
 @code{revert-buffer-function}.  @xref{Definition of
 revert-buffer-function,, Reverting, elisp, the Emacs Lisp Reference Manual}.
 
-In addition, it must have a @code{buffer-stale-function}.
+In addition, it must have a suitable @code{buffer-stale-function}.
 
 @c FIXME only defvar in all of doc/emacs!
 @defvar buffer-stale-function
-The value of this variable is a function to check whether a non-file
+The value of this variable is a function to check whether a
 buffer needs reverting.  This should be a function with one optional
 argument @var{noconfirm}.  The function should return non-@code{nil}
 if the buffer should be reverted.  The buffer is current when this
@@ -132,7 +132,7 @@ If you just want to automatically auto-revert every
 @code{auto-revert-interval} seconds (like the Buffer Menu), use:
 
 @example
-(set (make-local-variable 'buffer-stale-function)
+(setq-local buffer-stale-function
      #'(lambda (&optional noconfirm) 'fast))
 @end example
 
diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 456c2cbdc12..1fb664893f8 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -2,6 +2,8 @@
 
         * backups.texi (Making Backups, Reverting):
         Update for default values of some -function vars no longer being nil.
+        (Reverting): Update for buffer-stale-function
+        also applying to file-buffers.
 
 2014-03-25  Eli Zaretskii  <eliz@gnu.org>
 
diff --git a/doc/lispref/backups.texi b/doc/lispref/backups.texi
index 9fa97fc1300..63f8f227c84 100644
--- a/doc/lispref/backups.texi
+++ b/doc/lispref/backups.texi
@@ -764,7 +764,9 @@ may or may not run this hook.
 @c FIXME?  Move this section from arevert-xtra to here?
 @defvar buffer-stale-function
 The value of this variable specifies a function to call to check
-whether a non-file buffer needs reverting
+whether a buffer needs reverting.  The default value only handles
+buffers that are visiting files, by checking their modification time.
+Buffers that are not visiting files require a custom function
 @iftex
 (@pxref{Supporting additional buffers,,, emacs-xtra,  Specialized Emacs Features}).
 @end iftex